Symbols in computer programs are not necessarily isomorphic in form or capability to neural processes. Representations in our models are stored descriptions of the world and human behavior, created by a human interpreter; representations in the brain are neither immutable forms nor encoded in some language. Although the term " symbol " can be usefully applied to describe words, smoke signals, neural maps, and graphic icons, a science of symbol processing requires distinguishing between the structural, developmental, and interactive nature of different forms of representing.